In general, vehicles, such as motor vehicles, have an airbag device mounted therein. The airbag is inflated and deployed inside the vehicle to absorb an impact force applied to an occupant in emergency, such as collision or sudden deceleration. Such an airbag device generally includes an airbag that is normally folded and is inflated and deployed in emergency, an inflator for supplying gas to the airbag, a retainer for fixing the airbag and the inflator, and an airbag cover that covers the airbag.
In case of collision of the vehicle and sudden deceleration, gas is supplied from the inflator to the airbag and, thus, the airbag is inflated. Accordingly, the airbag cover is torn open and, thus, the airbag is released into the interior of the vehicle and is further inflated and deployed. In particular, a passenger airbag is inflated and deployed inside a space formed by an instrument panel, a windshield (a front window), and a passenger.
Note that in general, the retainer is made of a metallic material in order to withstand mechanical shock occurring when the airbag is inflated and deployed or the passenger collides with the airbag (refer to, for example, Japanese Unexamined Patent Application Publication No. 2001-097162 A). In an airbag device described in Japanese Unexamined Patent Application Publication No. 2001-097162 A, a retainer made from a sheet metal is fixed to part of the instrument panel using an attachment bolt.
In addition, in order to reduce the weight of a retainer, part of the retainer is made of a synthetic resin (refer to, for example, Japanese Unexamined Patent Application Publication No. 2000-326813 A). In an airbag device described in Japanese Unexamined Patent Application Publication No. 2000-326813 A, a retainer lower that supports an inflator is made of metal, and a retainer upper that supports an airbag is made of a synthetic resin. The retainer lower is fixed to the retainer upper using a bolt. By fitting a protrusion into an airbag cover (a lid), the retainer upper is fixed to the airbag cover. By employing such a structure, the weight of the retainer is reduced due to the retainer upper, and a shock is absorbed by the retainer lower.
As described above, in general, the retainer is fixed to the instrument panel or the airbag cover by using a fastener, such as a rivet or a bolt, or by fitting a protrusion into the instrument panel or the airbag cover. In recent years, as described in Japanese Patent No. 3822578 B2, in many cases, by relatively movably engaging a hook provided on a retainer with an opening formed in an airbag cover (a lid), the retainer is located in a floating manner. Such a structure reduces a shock of the airbag. In addition, the structure facilitates an assembling operation.